Power controls of electrically heat appliances particularly cooking plates

ABSTRACT

Power controls for electrically heated appliances, such as cooking plates. An energy control element in the power controls with a bimetallic member which has a control heating element and a contactor which influences the control heating element therein.

United States Patent Inventors Appl. No Filed Patented Priority GerhardGoessler Moerikestrasse 46, Oberderdingen Wurttenburg;

Robert Kieherer, 1m Bergfeld 33, Knlttlingen Wurttenberg, both of,Germany Apr. 1 l, 1968 June 22, 1971 Apr. 14, 1967 GermanyE33790VIld/21h POWER CONTROLS OF ELECTRICALLY HEAT APPLIANCESPARTICULARLY COOKING PLATES 10 Claims, 10 Drawing Figs.

U.S.Cl. 337/103, 2l9/51l,337/105 lnt.Cl H01h 37/12,

HOlh 61/013, HOSb 1/02 [50] Field ofSearch 337/3, 102,103,104,105,107,l00, 377; 219/442, 449, 450, 452, 511, 441, 448, 490

[56] References Cited UNITED STATES PATENTS 2,847,554 8/1958 Huffman219/442 2,763,750 9/1956 Adams et al.... 337/104 (X) 2,448,289 8/1948Anderson 219/51 1 2,399,423 4/1946 Bletz 219/449 (X) 2,354,918 8/1944Kearsley 219/511 Primary Examiner-Bernard A. Gilheany AssistantExaminer-Dewitt M. Morgan r1!I(H'H( Sparrow and Sparrow ABSTRACT: Powercontrols for electrically heated appliances, such as cooking plates. Anenergy control element in the power controls with a bimetallic memberwhich has a control heating element and a contactor which influences thecontrol heating element therein.

PATENTEnJunzzasn 3587.023

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sum 3 0F 4 INVENTORS a l Sparrow W row ATTORNEYS POWER CONTROLS OFELECTRICALLY HEAT APPLIANCES PARTICULARLY COOKING PLATES BACKGROUND OFTHE INVENTION The invention relates to electrically heated appliancessuch as cooking plates and particularly to power controls for theseappliances.

Power controls of this kind are known in which both the controls for thepower and the contactor, switch the power feed off the electricallyheated appliance.

SUMMARY This invention is based on the problem to reduce the amount ofthe costs for such controls. This problem is solved according to theinvention in such manner that the control heating of the power controlsis operated by the voltage of the appliance and that the power controlsthemselves switch only the power feed for the electrically heatedappliance; whereas the contactor only feeds control contacts. Thus, onlyone single heavy-duty switch must be provided for a high switchingpower, that is one with a powerful instantaneous toggle switch mechanismand with costly contacts. The contacts of the contactor which have onlyto switch the low load of the control heating means can make creepingcontacts and may be made of a less precious material, that is, may bemanufactured less expensively.

The contactor may switch dependent upon the temperature from theelectrically heated appliance, for example consisting of an overheatprotecting switch or of an adjustable temperature controller. But is isalso possible to use a time relay as a contactor which becomes effectivewhen the electrically heated appliance is switched on.

It is preferred to'add an additional resistor to the heating resistor onthe bimetallic member of the control heating, which can be switched bythe contactor in the sense of an increase of the power of the controlheating. The power which is fed to the cooking plate may be varied bycorresponding dimensioning of the two heating resistors.

The invention is further described in detail referring to severalexamples of preferred embodiments.

In its preferred embodiments, the invention is a power control devicefor electrically heated appliances, such as cooking plates. The controldevice has power controller embodying a bimetallic member with controlheating resistor means and has a contactor influencing the said means;the contactor having control contacts. The control heating of the powercontroller is operated with the appliance voltage and by the powercontroller switching only the power feed to the electrically heatedappliance, whereas the contactor operates only the control contacts. Theoperation of the contactor is dependent on the temperature of theelectrically heated appliance and preferably consists of a fixedlyadjusted overheat protection switch and timing means becoming activatedat switching on the electronically heated appliance. There may beprovided two followup contacts, the contactor being built as anadjustable temperature controller operating the two followup contacts,the contactor being built as an adjustable temperature controlleroperating the two followup contacts whereby one of the two contactsreacting on a lower temperature renders the control heating of the powercontroller efi'ective and whereby the other one of said contactsreacting on a higher temperature switches the control heating over tocontinuous duty. There may be provided a control shaft having aplurality of cams and an expansion member in the temperature controller,the two followup contacts being arranged to be set against the expansionmember by said cams independently of one another.

The heating resistor of the control heating on the abovementionedbimetallic member may have an auxiliary resistor arranged to be switchedby said contactor for increasing the power of said control heating, theauxiliary resistor being connected with the heating resistor of thecontrol heating in series and being arranged to be short-circuited bysaid contactor, the auxiliary resistor being also attached to thebimetallic member and separately arranged from the latter and arrangedto be switched in parallel to said heating resistor by said contactor.

There may be further provided a compensating bimetallic member, theauxiliary resistor being attached to the compensating bimetallic memberand being arranged'to be switched parallel to said heating resistor onsaid bimetallic member by the contactor; also hand-operated adjustingmeans, the auxiliary resistor arranged to be operated independently ofsaid contactor in the lower adjusting range of the power controller bysaid adjusting means in the sense of an increase of the control power. I

The power control deviceaccording to an embodiment of the invention isprovided'with a second bimetallic member, the auxiliary resistor beingattached thereto and being independent of the adjusting means of thepower controller, the second bimetallic member arranged to be switchedparallel to the heating resistor of the first bimetallic member by saidcontactor, whereby both bimetallic members are adapted to act separatelyon said switch controlling the power feed to the electrically heatedappliance.

As a further embodiment the power control device has a hot wire arrangedbefore said control heating of the power controller, the hot wireadapted to increase the power of said control heating dependent upon theduration of the switched time. The device also has a further resistor,the switch controlling the power feed to the electrically heatedappliance switching the further resistor before the hot wire by way of achangeover contact when the switch disconnects the power feed to theappliance, the size of the further resistor corresponding to saidswitched-off heating resistor of the control heating. The contactor mayconsists of a timer arranged to start running when the appliance isswitched on.

BRIEF DESCRIPTION OF THE DRAWINGS Like reference characters denote likeparts in the several figures of the drawing, in which FIGS. 1 to 10 showvarious embodiments by which the invention may be realized.

DESCRIPTION OF PREFERRED EMBODIMENTS In the embodiment shown in FIG. 1,the bimetallic member 1 which has the control heating means and anunheated bimetallic member 2 are fastened approximately parallel to oneanother on a support 3 which can be rotated about a shaft 4. The controlheating means of bimetallic member 1 consists of two heating resistors 5and 6. Heating resistor 6 will be hereinafter defined as an auxiliaryresistor. Both heating resistors are arranged on bimetallic member 1 inthe embodiment shown in FIG. 1. The splitting of the control heatingmeans on the bimetallic element is achieved in the simplest manner bytapping the continuous resistor coil on a clamp 7 which is arranged onit. Bimetallic member 1 influences a switch 8 which is arranged in thecircuit of the appliance heater 9, for example of the heating coil of anelectric cooking plate. Heating control resistors 5, 6 are switched inparallel to appliance heaters 9 and thus is operated with the appliancevoltage of 200 volts, for example. Therefore, they have a very highresistance according to their small power of a few watts. Auxiliaryresistor 6 which is switched in series with heating resistor 5 can beshort-circuited by a contact 10 which is influenced by the temperatureof the electrically heated apthe position of adjusting shaft 11,workload bimetallic member 1 is moved by the cam 13 more or less towardpower switch 8, and it can open switch 8 sooner or later or not at allwhen the control heating means is switched on. Appliance heaters 9 andcontrol heating of the power controls are switched off when switch 8 isopened. Bimetallic member I can then close again switch 8 after acooling period and can switch anew appliance heaters 9 and heatingcontrols 5,6. Corresponding to the proportion of switched-on time toswitched-off time in the operating cycle, which depends on positioningof bimetallic system 1, 2, 3 relative to switch 8, the actual power feedto electrical heating appliance 9 is adjusted. If then auxiliaryresistor 6 is short-circuited by contactor 10 when a certain temperatureof the electrically heated appliance is reached, heat resistor which hadbeen arranged in series up to this point, is switched on alone and theeffect of the control heating is increased. The consequence thereof isthat bimetallic element 1 is bent more toward switch 8 and theproportion of switched-on time to switched-off time is diminished,whereby the power feed to the electrically heated appliance is reduced.When contactor is reopened because the temperature of the electricallyheated appliance decreases correspondingly, the original startingcondition is temporarily reinstated.

Switch 8 alone switches the power feed to electrically heated appliance9 and therefor is designed for a heavy-duty switch work. Contactor 10switches only the power of the control heating comprising a few wattsand can therefor be equipped with inexpensive contacts for creepingoperation. It is designed in the embodiment of FIG. 1 as an overheatprotecting switch, attached to the electrically heated appliance, in theform of an instantaneously contacting bimetallic member through whichthe control voltage passes. Since the resistance of the control heatingis very high, that is several kiloohms, a change of the contactresistance at the contacts of contractor 10, which may be of the orderof magnitude of several ohms, is practically without influence.

Auxiliary resistor 6 also may be arranged at another point instead atworkload bimetallic member 1. The mode of operation is not changedthereby.

In the example of an embodiment shown in FIG. 2, auxiliary resistor 6 isswitched parallel to heating resistor 5, whereby contactor 10 alsocloses when the temperature on electrically heated appliance 9 rises.Auxiliary resistor 6 can be switched on by contactor 10. Thus, heatingresistor 5 is alone switched on and auxiliary resistor 6 will beswitched additionally in parallel by contactor 10 so that the power ofthe control heating is increased and the power feed to the electricallyheated appliance is reduced. In this case, auxiliary resistor 6 must bearranged on bimetallic member I.

The embodiment shown in FIG. 3 differs from the example shown in FIG. 2in that auxiliary resistor 6 is attached to compensating bimetallicmember 2 and that contactor 10 opens at increasing temperature of theelectrically heated appliance. The effect is basically the same. Whencontactor 10 switches off auxiliary resistor 6, bimetallic element 2bends away from bimetallic element 1. The result is that system 1, 2, 3swings closer to power switch 8, thereby diminishing the proportionbetween switched-on time and switched-off time and reducing theeffective power feed to the electrically heated appliance.

FIG. 4 shows the same arrangement as FIG. I. There is an additionalswitch provided which can be operated from adjustment shaft 11 by way ofa cam 14. Switch 15 can short circuit auxiliary resistor 6 independentlyof contactor l0. Cam 14 is designed in such fashion that switch 15 isclosed in a lower portion of the control range so that the maximumpossible control heating may be switched on in this range achievingthereby a small effective power of the electrically heated appliance.

In the example shown in FIG. 5 a single heating resistor 5 is onlyarranged on workload bimetallic member 1. Compensating bimetallic member2 on which cam 13 of adjusting shaft 11 operates in the manner asdescribed above, is not heated. A

second workload bimetallic member with a heating'resistor 17 isadditionally provided, which can open switch 8 independently of workloadbimetallic member 1. Bimetallic member 16 is stationarily clamped by oneof its ends and therefor cannot be influenced by the adjusting shaft.

Heating resistor 5 on workload bimetallic member 1 is constantlyswitched on so that switch 8 cycles according to the position ofadjusting shaft 11 in a corresponding proportion between switched-ontime and switched-off time. When now heating resistor 17 of bimetallicmember 16 is switched on in parallel to heat resistor 5 bytemperature-dependent contactor 10, bimetallic member 16 will openswitch 8 or keeps it in the open position if it had been already openedby bimetallic member I. Therewith the power feed to the electricallyheated appliance is determined by the heating of bimetallic member 16.

The power controls which have been described above, are operated in suchmanner that the power which has been selected on adjustment shaft 11, iscontrolled from the start of the switching, disregarding the negligiblyshort time which the bimetallic member requires for being heated fromthe ambient temperature to the working temperature. It is frequentlydesired to prevent the cycling for a certain period of time after thefirst switching-on of the power controls, so that the full power is fedto the electrically heated appliance resulting in a short heating-uptime.

This is made possible in the example shown in FIG. 6 by arranging a hotwire 20 before heating resistor 5 of bimetallic member 1 in thecircuitry corresponding to FIG. 5 and by branching ofl a wire 21 betweenhot wire 20 and the heating resistor. Wire 21 is connected to areversing contact 22 of switch 8 and contains a resistor 23.

When now the power controls are switched on, at first a weak currentflows only through heating resistor 5 of bimetallic member 1 which is byfar not sufficient for operating switch 8. Hot wire 20 is slowly heatedby the flowing current so that its resistance decreases gradually. Inthe same proportion the power of the control heating increases untileventually the control power climbs up to its full value after the stateof balance has been reached and until the power control cycles in theusual manner corresponding to the setting of adjustment shaft 11. Whenthen contactor 10 is closed, heating resistor 17 of bimetallic member I6is switched on. The result is that almost instantaneously switch 8disconnects the electrically heated appliance and heating resistor 5 andswitches it over to contact 22 provided that this had not already beenmade by bimetallic member I. The resistor 23 in wire 21 corresponds toheating resistor 5. Thus the current flowing through hot wire 20 remainsthe same after heat resistor 5 has been switched otT. Thus, hot wire 20retains its temperature which it had reached up to the switching timeand remains ineffective for the ensuing time period so that the start ofthe cycling is not retarded after switch 8 has been switched back.

A further example is shown in FIG. 7 in which contactor 10 is formed byan adjustable temperature controller which is coordinated with theelectrically heated appliance. The electrically heated applianceconstitutes therein a cooking plate and the temperature controller is ahydraulic controller having a disclike temperature feeler 25, whichabuts in the known manner within a central opening of the body 26 of thecooking plate at the bottom of the utensil which is placed on thecooking plate. The expanding member 28 of the controller, shaped like amembrane box, which is connected with feeler 25 by a capillary 27, actson two contacts 29 and 30, which close successively when the feelertemperature rises. The temperature is adjustable by way of a cam whichis arranged on adjustment shaft 11 of the power control, depending uponthe heating power which is selected on the power control. The cam actson expanding member 28, which is for example, rotatable about a shaft32, and determines the stroke of the membrane up to the operation ofcontacts 29 and 30.

In the same manner as in the examples shown in FIGS. 5 and 6, a heatingresistor 5 is coordinated to workload bimetallic member 1, and anauxiliary resistor 17 is coordinated to an auxiliary workload bimetallicmember 16. Both bimetallic members act on switch 8 which controls thepower feed to electrically heated appliance 9. Contact 29, which isinfluenced by the lower feeler temperature, is arranged before heatingresistor 5, and contact 30, which is influenced by the higher feelertemperature, is arranged before heating resistor 17.

When adjustment shaft 11 of the power control is rotated away from theOK position, switch 8 is closed. Contacts 29 and 30 which are influencedby contactor 10, are open. Therefore, heating resistors 5 and 17 remainwithout voltage at first. Thus the full heating powerwill be fed to theelectrically heated appliance, disregarding the position of adjustmentshaft 11. When contact 29 of the temperature controller is closed,heating resistor 5 of bimetallic member 1 is switched on. The result isthat the power control on switch 8 cycles the heating power which hasbeen selected on adjustment shaft 11. When then contact 30 is closed,because the temperature on feeler 25 still increased, heating resistor17 of bimetallic member 16 will be also switched on. Under the increasedpower of the control heating, switch 8 is kept open, regardless of thecycling position which it had held at that instance. The heating currentof electrically heated appliance 9 is then entirely switched off and itis only switched on again, when the temperature on feeler 25 has droppedso far that the second contact 30 of the temperature controller opensagain. At that time the power which had been adjusted on the powercontrol for cycling, will be fed to the electrically heated appliance.If the temperature on feeler 25 drops further, contact 29 also will openresulting in the appliance being operated again with the utmostpossiblepower.

In FIG. 8 an identically operating embodiment with a single workloadbimetallic member 1 and with a single heating resistor 5 whichisarranged on it, is shown. The contactor is a hydraulic temperaturecontroller, as it is in FIG. 7, with a discshaped temperature feeler andwith an expansion member which is connected with feeler 25 and with anexpansion member which is connected with feeler 25 by a capillary tube,which operates two contacts 29 and 30 which operate in successive order.Both contacts 29 and 30 are connected with heating resistor 5 in series.Contact 29 which closes at the lower feeler temperature, is closed forswitching of the heating resistor 5 of bimetallic member 1 when thefeeler temperature rises above the nominal value, whereas contact 30switches at a slightly higher feeler temperature 5 to a contact 34 towhich a wire 35 is connected bridging power switch 8. Contact 30 mustact snappingly in order to switch over momentarily. Otherwise thisexample is equivalent to the example shown in FIG. 7.

When contact 29 of the temperature controller is closed, heatingresistor 5 of bimetallic member 1 is switched on and the power controlcycles on switch 8 the preselected power.

, When eventually contact 30 switches over to contact 34, re-

sistor 5 of the control heating remains permanently switched on becauseswitch 8 is bridged by wire 35. The result is that switch 8 remainsswitched off until contact 30 will be switched back again when thetemperature on feeler 25 has dropped correspondingly.

Contact 29 which acts at the lower temperature, can be bridged by anauxiliary resistor 6 as it is shown in FIG. 8. Then a current flows fromthe start through heating resistor 5 of bimetallic member 1, whichcurrent is so much weakened by the additional auxiliary resistor, thatswitch 8 according to the setting of the temperature controller does notcycle any power or a considerably larger one than the one which has beenset on the power control. When contact 29 is closed, auxiliary resistor6 is short-circuited. Then the current flows only through heatingresistor 5, so that the power of the control heating is increased to thevalue by which the power is cycled which has been set on the powercontrol. In the examples shown in FIGS. 7 and 8 a fixed difference ofthe operating temperatures has been adjusted between the contacts 29 and30 which are acted upon by the temperature controller. According to FIG.9 both contacts 29 and 30 are independently adjustable from one anotherby cams 37 and 38 of an adjustment shaft 39 against the fixedly arrangedexpansion member 28 of the temperature controller. The supports 40 and41 of contacts 29 and 30 are independently rotatable from one anotherabout a common fixed shaft 42. Switching pins 43 and 44 of both contacts29 and 30 cooperate with a tilting member 45 which is moved by theexpansion member 28 of the temperature controller.

By these means the difference between the operating temperatures of bothcontacts 29 and 30 can be varied at will over the adjustment range; forexample it can be enlarged with increasing heating power. This is, forexample, advantageous for broiling operations. In this case it is usefulto have a relatively large difference between the operating temperaturesso that during the impulse-shaped power feed which starts after theacting of contact 29, a sufficiently large temperature range isavailable, within which the median power is fed which has been set onthe power control without action of contact 30 interrupting the powerfeed to the cooking plate. Obviously, it is presumed that the correctmedian power has been set for the corresponding temperature, whichpermits a smooth broiling.

According to FIG. I0 the contactor 10 is a timer 50 which has anadjustment shaft 51 and which operates a contact 52 for a heatingresistor 5 which is coordinated to the workload bimetallic member I.Timer 50 is switched on together with the power control and closescontact 52 after the preset time period. Thereby heating resistor 5 getsvoltage and the power control cycles on switch 8 the power which is fedto electrically heated appliance 9 with the frequency corresponding tothe setting. Starting from the switching of the power control up to theoperating of contact 52, the electrically heated appliance is operatedwith full power.

In this case an auxiliary resistor 6 also can be coordinated with theheating resistor 5 on bimetallic member 1, which is either attached tothe latter-or which is separately arranged therefrom and which isswitched on or off by contact 52.

While the invention has been described and illustrated with respect tocertain preferred examples which give satisfactory results, it will beunderstood by those skilled in the art after understanding the principleof the invention, that various changes and modifications may be madewithout departing from the spirit of the invention.

We claim:

1. Power control device for an electrically heated appliance such as acooking plate, said appliance operated by a voltage, said control devicecomprising a power controller, said power controller including abimetallic member and switch means actuated by said bimetallic member, acontrol heating resistor on said member, said resistor disposed forapplying heat to said member, said member disposed to act on said switchmeans for switching the power feed on to said appliance, said resistorbeing energized only when said power is fed to said appliance, saidcontrol device further comprising an auxiliary resistor located on saidcontrol heating resistor, a contactor having control contacts, saidcontactor including means dependent on the temperature of saidappliance, said means actuating said control contacts, said auxiliaryresistor arranged in series with said control heating resistor, saidcontactor having contacts connected in parallel with said auxiliaryresistor, said contacts being closed for increasing the heating powerapplied to said bimetallic member when the temperature of said ap'pliance increases. I

2. Power control device according to claim 1, and having hand-operatedpower adjusting means, said adjusting means having contacts, saidcontacts being connected in parallel with said means dependent ontemperature whereby movement of said hand-operated adjusting .meansmanually positions said contacts for shortcircuiting said resistorindependently of said contactor.

3. Power control device for an electrically heated appliance such as acooking plate, said appliance operated by a voltage, said control devicecomprising a power controller, said power controller including abimetallic member, a control heating resistor on said member, saidresistor disposed for applying heat to said member, said member disposedto act on said switch means for switching the power feed on to saidappliance, said resistor being energized only when said power is fed tosaid appliance, said control device further comprising an auxiliaryresistor, said auxiliary resistor being separately disposed from saidbimetallic member, a contactor having control contacts, said contactorincluding means dependent on the temperature of said appliance, saidmeans actuating said control contacts, said auxiliary resistor arrangedin series with said control heating resistor, said contactor havingcontacts connected in parallel with said auxiliary resistor, saidcontacts being closed for increasing the heating power applied to saidbimetallic member when the temperature of said appliance-increases.

4. Power control device for an electrically heated appliance such as acooking plate, saidappliance operated by a voltage, said control devicecomprising a power controller, said power controller including abimetallic member and switch means actuated by said bimetallic member,acontrol heating resistor on said member, said resistor disposed forapplying heat to said member, said member disposed to' act on saidswitch means for switching the power feed on tosaid appliance,-saidresistor being energized only when said power is fed to said appliance,said control device further comprising an auxiliary resistor located onsaid bimetallic member, a contactor having control contacts, saidcontactor including means dependent on the temperature of saidappliance, said means actuating said control contacts, said auxiliaryresistor arranged in series with said control heating resistor, saidcontrol contacts of said contactor'electricallyconnected with saidauxiliary resistor and being disposed for switching off the latter forincreasing the heating power applied to said bimetallic member when'thetemperature of said appliance increases. i

5. Power control device for an electrically heated appliance such as acooking plate, said appliance operated by a voltage, said control devicecomprising a power controller, said power controller including abimetallic member and switch means actuated by said bimetallic member, acontrol heating resistor on said member,'said resistor disposed forapplying heat to said member, said member disposed to act on said switchmeans for switching the power feed'on to said appliance, said resistorbeing energized'only when said power is fed to said appliance, saidcontrol devicefurther comprising an auxiliary resistor, a compensatingbimetallic member secured to said member, said auxiliary resistor beingattached to said compensating bimetallic member, said auxiliary resistorbeing connected with said control heating resistor in parallel,aeontactor having control contacts, said contactor including meansdependent on the temperature of said appliance, said means actuatingsaid control contacts, said control contacts being electricallyconnected in series with said auxiliary resistor for switching thelatter into and out of parallel circuit with said control heatingresistor.

6. Power control device for an electrically heated appliance such as acooking plate, said appliance operated by a voltage, said control devicecomprising a power controller, said power controller including a firstbimetallic member and switch means actuated by said first bimetallicmember, a control heating resistor on said member, said resistordisposed for applying heat to said member, said member disposed to acton said switch means for switching the power feed on to saidappliance,said resistor being energized only when said power is fed to saidappliance, said control device further comprising an auxiliary resistor,a contactor having control contacts, and

' further having a second bimetallic member, said auxiliary resistorattached to said second bimetallic member, said auxiliary resistorhaving circuit means connecting said auxiliary resistor in series with,said control contacts, said contactor including means dependent on thetemperature of said appliance acting on said control contacts forswitching said auxiliary resistor in parallel with said control heatingresistor, whereby both bimetallic members are constructed for actingseparately on said switch controlling the power feed to said appliance.I I

7. Power control device for an electrically heated appliance such as acooking plate, said appliance operated by a voltage, said control devicecomprising a power controller, said power controller including a firstbimetallic member and switch means actuated by said first bimetallicmember, a control heating resistor on said member, said resistordisposed for applying heat to said member, said member disposed to acton said switch means for switching the power feed onto said appliance,said resistor being energized only when said power is fed to saidappliance, said control device further comprising an auxiliary resistorlocated on a second bimetallic member disposed for actuating said switchindependently of said first bimetallic means, a contactor having controlcontacts, said contactor including means dependent-on the temperature ofsaid appliance, said means actuating said control contacts, saidauxiliary resistor arranged in parallel with said control heatingresistor, said contactor having contacts connected in series withsaidauxiliary resistor, said contacts being closed for increasing heatingpower applied to said bimetallic member when the temperature of saidappliance increases, a hot wire placed in series before said controlheating resistor, said hot wire disposed to increase the heating powerof said control heating resistor by decreasing its resistance whilebecoming hot, and a further resistor placed between said powercontroller and said hot wire, said controller controlling the power feedto said appliance and further switching-on said further resistor inseries with said hot wire by way of a changeover contact when saidcontroller disconnects said power feed to said appliance, said furtherresistor having a size corresponding to said switched-off controlheating resistor.

8. Power control device for an electrically heated appliance,

such as a cooking plate, appliance operated by a voltage,

said control device comprising a power controller, said power controllerincluding a bimetallic member and switch means actuated by saidbimetallic member, said member having a control heating resistor, acontactor in said control device, control contacts on said contactor,said control contacts being in electrical series with said resistor,said resistor being adapted to operate with said appliance voltage, saidcontroller adapted to switch only the power to said appliance, whilesaid contactor operates only said control contacts and switches only thepower for operating said controller, said contactor includingmeansdependent on the temperature of said appliance for controlling theoperation of said control contacts when the temperature of saidappliance increases, said contactor further including followup contacts,said followup contacts being electrically connected in series with saidcontrol heating resistor, said control contacts and said followupcontacts disposed for operating in successive order, one of said twocontacts being operated by said means dependent on the temperaturecontroller at a lower temperature rendering said con- ,trol heating ofsaid power controller effective and the other one of said contacts beingoperated by said means dependent on the temperature of said appliance ata higher temperature, switching said control heating resistor over tocontinuous duty, and manual adjusting means for positioning said controlcontactor and said followup contacts independent of each otherandadjustingthe temperature points at which said followup contacts areoperated by said means dependent on the temperature of said appliance,

9. Power control device according to claim 8, having a control shaft, aplurality of cams on said shaft, and said means dependent on thetemperature of said appliance having an expansion member, said camssetting said two contacts against said expansion member independently ofone another.

10, Power control device for an electrically heated appliance such as acooking plate, said appliance operated by a voltage, said control devicecomprising a power controller having a switch means and a bimetallicmember thereon, said member having a control heating resistor forapplying heat to said member, said member mechanically connected to saidswitch means for switching on the power feed to said appliance, saidresistor being energized alternatingly only when power is fed to saidappliance, said control device further comprising a contactor havingcontrol contacts thereon, said 10 to said control heating resistor anddisposed for energizing said resistor with said voltage after saidadjusting adjusted time period has elapsed, said control device furthercompriscontactor consisting of a manually adjustable timer, said timer 5mg manually operable means for pwotany adjustmg Said disposed forrunning for a preset time period when said appliance is switched on,said timer being electrically connected bimetallic member in relation tosaid switch means.

1. Power control device for an electrically heated appliance such as acooking plate, said appliance operated by a voltage, said control devicecomprising a power controller, said power controller including abimetallic member and switch means actuated by said bimetallic member, acontrol heating resistor on said member, said resistor disposed forapplying heat to said member, said member disposed to act on said switchmeans for switching the power feed on to said appliance, said resistorbeing energized only when said power is fed to said appliance, saidcontrol device further comprising an auxiliary resistor located on saidcontrol heating resistor, a contactor having control contacts, saidcontactor including means dependent on the temperature of saidappliance, said means actuating said control contacts, said auxiliaryresistor arranged in series with said control heating resistor, saidcontactor having contacts connected in parallel with said auxiliaryresistor, said contacts being closed for increasing the heating powerapplied to said bimetallic member when the temperature of said applianceincreases.
 2. Power control device according to claim 1, and havinghand-operated power adjusting means, said adjusting means havingcontacts, said contacts being connected in parallel with said meansdependent on temperature whereby movement of said hand-operatedadjusting means manually positions said contacts for shortcircuitingsaid resistor independently of said contactor.
 3. Power control devicefor an electrically heated appliance such as a cooking plate, saidappliance operated by a voltage, said control device comprising a powercontroller, said power controller including a bimetallic member, acontrol heating resistor on said member, said resistor disposed forapplying heat to said member, said member disposed to act on said switchmeans for switching the power feed on to said appliance, said resistorbeing energized only when said power is fed to said appliance, saidcontrol device further comprising an auxiliary resistor, said auxiliaryresistor being separately disposed from said bimetallic member, acontactor having control contacts, said contactor including meansdependent on the temperature of said appliance, said means actuatingsaid control contacts, said auxiliary resistor arranged in series withsaid control heating resistor, said contactor having contacts connectedin parallel with said auxiliary resistor, said contacts being closed forincreasing the heating power applied to said bimetallic member when thetemperature of said appliance increases.
 4. Power control device for anelectrically heated appliance such as a cooking plate, said applianceoperated by a voltage, said control device comprising a powercontroller, said power controller including a bimetallic member andswitch means actuated by said bimetallic member, a control heatingresistor on said member, said resistor disposed for applying heat tosaid member, said member disposed to act on said switch means forswitching the power feed on to said appliance, said resistor beingenergized only when said power is fed to said appliance, said controldevice further comprising an auxiliary resistor located on saidbimetallic member, a contactor having control contacts, said contactorincluding means dependent on the temperature of said appliance, saidmeans actuating said control contacts, said auxiliary resistor arrangedin series with said control heating resistor, said control contacts ofsaid contactor electrically connected with said auxiliary resistor andbeing disposed for switching off the latter for increasing tHe heatingpower applied to said bimetallic member when the temperature of saidappliance increases.
 5. Power control device for an electrically heatedappliance such as a cooking plate, said appliance operated by a voltage,said control device comprising a power controller, said power controllerincluding a bimetallic member and switch means actuated by saidbimetallic member, a control heating resistor on said member, saidresistor disposed for applying heat to said member, said member disposedto act on said switch means for switching the power feed on to saidappliance, said resistor being energized only when said power is fed tosaid appliance, said control device further comprising an auxiliaryresistor, a compensating bimetallic member secured to said member, saidauxiliary resistor being attached to said compensating bimetallicmember, said auxiliary resistor being connected with said controlheating resistor in parallel, a contactor having control contacts, saidcontactor including means dependent on the temperature of saidappliance, said means actuating said control contacts, said controlcontacts being electrically connected in series with said auxiliaryresistor for switching the latter into and out of parallel circuit withsaid control heating resistor.
 6. Power control device for anelectrically heated appliance such as a cooking plate, said applianceoperated by a voltage, said control device comprising a powercontroller, said power controller including a first bimetallic memberand switch means actuated by said first bimetallic member, a controlheating resistor on said member, said resistor disposed for applyingheat to said member, said member disposed to act on said switch meansfor switching the power feed on to said appliance, said resistor beingenergized only when said power is fed to said appliance, said controldevice further comprising an auxiliary resistor, a contactor havingcontrol contacts, and further having a second bimetallic member, saidauxiliary resistor attached to said second bimetallic member, saidauxiliary resistor having circuit means connecting said auxiliaryresistor in series with said control contacts, said contactor includingmeans dependent on the temperature of said appliance acting on saidcontrol contacts for switching said auxiliary resistor in parallel withsaid control heating resistor, whereby both bimetallic members areconstructed for acting separately on said switch controlling the powerfeed to said appliance.
 7. Power control device for an electricallyheated appliance such as a cooking plate, said appliance operated by avoltage, said control device comprising a power controller, said powercontroller including a first bimetallic member and switch means actuatedby said first bimetallic member, a control heating resistor on saidmember, said resistor disposed for applying heat to said member, saidmember disposed to act on said switch means for switching the power feedonto said appliance, said resistor being energized only when said poweris fed to said appliance, said control device further comprising anauxiliary resistor located on a second bimetallic member disposed foractuating said switch independently of said first bimetallic means, acontactor having control contacts, said contactor including meansdependent on the temperature of said appliance, said means actuatingsaid control contacts, said auxiliary resistor arranged in parallel withsaid control heating resistor, said contactor having contacts connectedin series with said auxiliary resistor, said contacts being closed forincreasing heating power applied to said bimetallic member when thetemperature of said appliance increases, a hot wire placed in seriesbefore said control heating resistor, said hot wire disposed to increasethe heating power of said control heating resistor by decreasing itsresistance while becoming hot, and a further resistor placed betweensaid power controller and said hot wire, said controller controlling thepoWer feed to said appliance and further switching-on said furtherresistor in series with said hot wire by way of a changeover contactwhen said controller disconnects said power feed to said appliance, saidfurther resistor having a size corresponding to said switched-offcontrol heating resistor.
 8. Power control device for an electricallyheated appliance, such as a cooking plate, said appliance operated by avoltage, said control device comprising a power controller, said powercontroller including a bimetallic member and switch means actuated bysaid bimetallic member, said member having a control heating resistor, acontactor in said control device, control contacts on said contactor,said control contacts being in electrical series with said resistor,said resistor being adapted to operate with said appliance voltage, saidcontroller adapted to switch only the power to said appliance, whilesaid contactor operates only said control contacts and switches only thepower for operating said controller, said contactor including meansdependent on the temperature of said appliance for controlling theoperation of said control contacts when the temperature of saidappliance increases, said contactor further including followup contacts,said followup contacts being electrically connected in series with saidcontrol heating resistor, said control contacts and said followupcontacts disposed for operating in successive order, one of said twocontacts being operated by said means dependent on the temperaturecontroller at a lower temperature rendering said control heating of saidpower controller effective and the other one of said contacts beingoperated by said means dependent on the temperature of said appliance ata higher temperature, switching said control heating resistor over tocontinuous duty, and manual adjusting means for positioning said controlcontactor and said followup contacts independent of each other andadjusting the temperature points at which said followup contacts areoperated by said means dependent on the temperature of said appliance.9. Power control device according to claim 8, having a control shaft, aplurality of cams on said shaft, and said means dependent on thetemperature of said appliance having an expansion member, said camssetting said two contacts against said expansion member independently ofone another.
 10. Power control device for an electrically heatedappliance such as a cooking plate, said appliance operated by a voltage,said control device comprising a power controller having a switch meansand a bimetallic member thereon, said member having a control heatingresistor for applying heat to said member, said member mechanicallyconnected to said switch means for switching on the power feed to saidappliance, said resistor being energized alternatingly only when poweris fed to said appliance, said control device further comprising acontactor having control contacts thereon, said contactor consisting ofa manually adjustable timer, said timer disposed for running for apreset time period when said appliance is switched on, said timer beingelectrically connected to said control heating resistor and disposed forenergizing said resistor with said voltage after said adjusting adjustedtime period has elapsed, said control device further comprising manuallyoperable means for pivotally adjusting said bimetallic member inrelation to said switch means.